Memory:The computer memory is a temporary storage area. It holds the data and instructions that the Central Processing Unit (CPU) needs. Before a program can be run, the program is loaded from some storage medium into the memory. This allows the CPU direct access to the program. Memory is a need for any computer.Types:-Memory is primarily of three types.a) Cache Memoryb) Primary Memory/Main Memoryc) Secondary Memory

Cache Memory:-Cache memory is a very high speed semiconductor memory which can speed up CPU. It acts as a buffer between the CPU and main memory. It is used to hold those parts of data and program which are most frequently used by CPU.

Primary Memory:-Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data is lost when power is switched off. It is divided into two subcategories: 1.RAM ( Random Access Memory ) 2.ROM ( Read Only Memory )

RAM:RAM memory is volatile in nature. The memory stored in the RAM is temporary and it will be lost when the power gets switched off.It is also called read/write memory because data can both be read and written in this memory.It is further divided into two different types: 1.DRAM (Dynamic Random Access Memory) 2.SRAM (Static Random Access Memory).DRAM: It holds data for short time period and will be refreshed periodically.SRAM: It holds data and refreshing does not required. It is faster than DRAM.

ROM:It is non volatile and the information stored in the ROM is permanent and will not be erased off during the power off.It is further classified into three types: 1.PROM ( Programmable Read Only Memory ) 2.EPROM ( Erasable Programmable Read Only Memory ) 3.EEPROM ( Electrically Erasable Programmable Read Only Memory )PROM: Programs or instructions written in PROM or ROM cannot be erased or changed.EPROM: Data written in EPROM chip can be erased by using special devices and ultraviolet rays.EEPROM: This kind of ROM can be written or changed with the help of electrical devices. So data stored can be easily modified.

Secondary Memory:- Secondary memory is external and permanent in nature.It is concerned with magnetic memory.It can be stored on storage media like floppy disks, magnetic disks, magnetic tapes. This memory can also be stored optically on Optical disks & CD-ROM.